// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * mpls tunnels An implementation mpls tunnels using the light weight tunnel
 *              infrastructure
 *
 * Authors:     Roopa Prabhu, <roopa@cumulusnetworks.com>
 */
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/net.h>
#include <linux/module.h>
#include <linux/mpls.h>
#include <linux/vmalloc.h>
#include <net/ip.h>
#include <net/dst.h>
#include <net/lwtunnel.h>
#include <net/netevent.h>
#include <net/netns/generic.h>
#include <net/ip6_fib.h>
#include <net/route.h>
#include <net/mpls_iptunnel.h>
#include <linux/mpls_iptunnel.h>
#include "internal.h"

static const struct nla_policy mpls_iptunnel_policy[MPLS_IPTUNNEL_MAX + 1] = {
        [MPLS_IPTUNNEL_DST]     = { .len = sizeof(u32) },
        [MPLS_IPTUNNEL_TTL]     = { .type = NLA_U8 },
};

static unsigned int mpls_encap_size(struct mpls_iptunnel_encap *en)
{
        /* The size of the layer 2.5 labels to be added for this route */
        return en->labels * sizeof(struct mpls_shim_hdr);
}

static int mpls_xmit(struct sk_buff *skb)
{
        struct mpls_iptunnel_encap *tun_encap_info;
        struct mpls_shim_hdr *hdr;
        struct net_device *out_dev;
        unsigned int hh_len;
        unsigned int new_header_size;
        unsigned int mtu;
        struct dst_entry *dst = skb_dst(skb);
        struct rtable *rt = NULL;
        struct rt6_info *rt6 = NULL;
        struct mpls_dev *out_mdev;
        struct net *net;
        int err = 0;
        bool bos;
        int i;
        unsigned int ttl;

        /* Find the output device */
        out_dev = dst->dev;
        net = dev_net_rcu(out_dev);

        if (!mpls_output_possible(out_dev) ||
            !dst->lwtstate || skb_warn_if_lro(skb))
                goto drop;

        skb_forward_csum(skb);

        tun_encap_info = mpls_lwtunnel_encap(dst->lwtstate);

        /* Obtain the ttl using the following set of rules.
         *
         * LWT ttl propagation setting:
         *  - disabled => use default TTL value from LWT
         *  - enabled  => use TTL value from IPv4/IPv6 header
         *  - default  =>
         *   Global ttl propagation setting:
         *    - disabled => use default TTL value from global setting
         *    - enabled => use TTL value from IPv4/IPv6 header
         */
        if (dst->ops->family == AF_INET) {
                if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
                        ttl = tun_encap_info->default_ttl;
                else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
                         !net->mpls.ip_ttl_propagate)
                        ttl = net->mpls.default_ttl;
                else
                        ttl = ip_hdr(skb)->ttl;
                rt = dst_rtable(dst);
        } else if (dst->ops->family == AF_INET6) {
                if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DISABLED)
                        ttl = tun_encap_info->default_ttl;
                else if (tun_encap_info->ttl_propagate == MPLS_TTL_PROP_DEFAULT &&
                         !net->mpls.ip_ttl_propagate)
                        ttl = net->mpls.default_ttl;
                else
                        ttl = ipv6_hdr(skb)->hop_limit;
                rt6 = dst_rt6_info(dst);
        } else {
                goto drop;
        }

        /* Verify the destination can hold the packet */
        new_header_size = mpls_encap_size(tun_encap_info);
        mtu = mpls_dev_mtu(out_dev);
        if (mpls_pkt_too_big(skb, mtu - new_header_size))
                goto drop;

        hh_len = LL_RESERVED_SPACE(out_dev);
        if (!out_dev->header_ops)
                hh_len = 0;

        /* Ensure there is enough space for the headers in the skb */
        if (skb_cow_head(skb, hh_len + new_header_size))
                goto drop;

        skb_set_inner_protocol(skb, skb->protocol);
        skb_reset_inner_network_header(skb);

        skb_push(skb, new_header_size);

        skb_reset_network_header(skb);

        skb->dev = out_dev;
        skb->protocol = htons(ETH_P_MPLS_UC);

        /* Push the new labels */
        hdr = mpls_hdr(skb);
        bos = true;
        for (i = tun_encap_info->labels - 1; i >= 0; i--) {
                hdr[i] = mpls_entry_encode(tun_encap_info->label[i],
                                           ttl, 0, bos);
                bos = false;
        }

        mpls_stats_inc_outucastpkts(net, out_dev, skb);

        if (rt) {
                if (rt->rt_gw_family == AF_INET6)
                        err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt->rt_gw6,
                                         skb);
                else
                        err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt->rt_gw4,
                                         skb);
        } else if (rt6) {
                if (ipv6_addr_v4mapped(&rt6->rt6i_gateway)) {
                        /* 6PE (RFC 4798) */
                        err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt6->rt6i_gateway.s6_addr32[3],
                                         skb);
                } else
                        err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt6->rt6i_gateway,
                                         skb);
        }
        if (err)
                net_dbg_ratelimited("%s: packet transmission failed: %d\n",
                                    __func__, err);

        return LWTUNNEL_XMIT_DONE;

drop:
        out_mdev = out_dev ? mpls_dev_rcu(out_dev) : NULL;
        if (out_mdev)
                MPLS_INC_STATS(out_mdev, tx_errors);
        kfree_skb(skb);
        return -EINVAL;
}

static int mpls_build_state(struct net *net, struct nlattr *nla,
                            unsigned int family, const void *cfg,
                            struct lwtunnel_state **ts,
                            struct netlink_ext_ack *extack)
{
        struct mpls_iptunnel_encap *tun_encap_info;
        struct nlattr *tb[MPLS_IPTUNNEL_MAX + 1];
        struct lwtunnel_state *newts;
        u8 n_labels;
        int ret;

        ret = nla_parse_nested_deprecated(tb, MPLS_IPTUNNEL_MAX, nla,
                                          mpls_iptunnel_policy, extack);
        if (ret < 0)
                return ret;

        if (!tb[MPLS_IPTUNNEL_DST]) {
                NL_SET_ERR_MSG(extack, "MPLS_IPTUNNEL_DST attribute is missing");
                return -EINVAL;
        }

        /* determine number of labels */
        if (nla_get_labels(tb[MPLS_IPTUNNEL_DST], MAX_NEW_LABELS,
                           &n_labels, NULL, extack))
                return -EINVAL;

        newts = lwtunnel_state_alloc(struct_size(tun_encap_info, label,
                                                 n_labels));
        if (!newts)
                return -ENOMEM;

        tun_encap_info = mpls_lwtunnel_encap(newts);
        ret = nla_get_labels(tb[MPLS_IPTUNNEL_DST], n_labels,
                             &tun_encap_info->labels, tun_encap_info->label,
                             extack);
        if (ret)
                goto errout;

        tun_encap_info->ttl_propagate = MPLS_TTL_PROP_DEFAULT;

        if (tb[MPLS_IPTUNNEL_TTL]) {
                tun_encap_info->default_ttl = nla_get_u8(tb[MPLS_IPTUNNEL_TTL]);
                /* TTL 0 implies propagate from IP header */
                tun_encap_info->ttl_propagate = tun_encap_info->default_ttl ?
                        MPLS_TTL_PROP_DISABLED :
                        MPLS_TTL_PROP_ENABLED;
        }

        newts->type = LWTUNNEL_ENCAP_MPLS;
        newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
        newts->headroom = mpls_encap_size(tun_encap_info);

        *ts = newts;

        return 0;

errout:
        kfree(newts);
        *ts = NULL;

        return ret;
}

static int mpls_fill_encap_info(struct sk_buff *skb,
                                struct lwtunnel_state *lwtstate)
{
        struct mpls_iptunnel_encap *tun_encap_info;

        tun_encap_info = mpls_lwtunnel_encap(lwtstate);

        if (nla_put_labels(skb, MPLS_IPTUNNEL_DST, tun_encap_info->labels,
                           tun_encap_info->label))
                goto nla_put_failure;

        if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT &&
            nla_put_u8(skb, MPLS_IPTUNNEL_TTL, tun_encap_info->default_ttl))
                goto nla_put_failure;

        return 0;

nla_put_failure:
        return -EMSGSIZE;
}

static int mpls_encap_nlsize(struct lwtunnel_state *lwtstate)
{
        struct mpls_iptunnel_encap *tun_encap_info;
        int nlsize;

        tun_encap_info = mpls_lwtunnel_encap(lwtstate);

        nlsize = nla_total_size(tun_encap_info->labels * 4);

        if (tun_encap_info->ttl_propagate != MPLS_TTL_PROP_DEFAULT)
                nlsize += nla_total_size(1);

        return nlsize;
}

static int mpls_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
{
        struct mpls_iptunnel_encap *a_hdr = mpls_lwtunnel_encap(a);
        struct mpls_iptunnel_encap *b_hdr = mpls_lwtunnel_encap(b);
        int l;

        if (a_hdr->labels != b_hdr->labels ||
            a_hdr->ttl_propagate != b_hdr->ttl_propagate ||
            a_hdr->default_ttl != b_hdr->default_ttl)
                return 1;

        for (l = 0; l < a_hdr->labels; l++)
                if (a_hdr->label[l] != b_hdr->label[l])
                        return 1;
        return 0;
}

static const struct lwtunnel_encap_ops mpls_iptun_ops = {
        .build_state = mpls_build_state,
        .xmit = mpls_xmit,
        .fill_encap = mpls_fill_encap_info,
        .get_encap_size = mpls_encap_nlsize,
        .cmp_encap = mpls_encap_cmp,
        .owner = THIS_MODULE,
};

static int __init mpls_iptunnel_init(void)
{
        return lwtunnel_encap_add_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
}
module_init(mpls_iptunnel_init);

static void __exit mpls_iptunnel_exit(void)
{
        lwtunnel_encap_del_ops(&mpls_iptun_ops, LWTUNNEL_ENCAP_MPLS);
}
module_exit(mpls_iptunnel_exit);

MODULE_ALIAS_RTNL_LWT(MPLS);
MODULE_SOFTDEP("post: mpls_gso");
MODULE_DESCRIPTION("MultiProtocol Label Switching IP Tunnels");
MODULE_LICENSE("GPL v2");